Radioreceiver



Aug. 12, 1930.

R. S. OHL

RADIO RECEIVER Filed Feb. 20. 1926 A TTURNE Y Patented Aug. 12, 1930 UNITED! .s1-Aires.'

PATENT v OFI-"lcs RUSSELL S. OHL, NEW YORK, N. Y., -ASSIGNOB. T() AMRICAN TELIEHONE AND TELE- GRVAPH COMPANY, A CORPORATON\0F NEW YORK BADIORECEIVEB Application med Februaryv 2o, 192s. .serial N0. 89,794,

This inventionl relates to radio receiving systems, and more particularly to methods of and means for controlling the output volume of the receiver.

5 In the radioreceiving system disclosed in the UnitedA States patent to Afel, No. 1,511,015, October 7, 1924, there is shown an arrangement for controlling the output vol uine of the receiver whereby a portion of the energy in the receiving channel is taken off after it has been passed through the detector and an amplifier and is then utilized to effect volume control in accordance with the iuctuations of the vcarrier'intensity, the energy in the branch path being rectified' and fed back to the grid of the detector to adjustv the biasing potential thereon 1and thus to control the gain. With such an arrangement there is the likelihood of singingin the system. 2o l It is applicants object to provide for the automatic maintenance of the outputvolume level iny spite of variations of thefcarrier intensity, and further, to accomplish this withl out the danger of singing in the receiving system.

Applicant also aims to provide a more reliable control of theoutput volume, and with this aim in view utilizes means new in this connection for selecting more sharply than has been done heretofore the carrier fre-` quency component which is to be rectified and impressed upon the. detector to effect the desired variation of grid potential.

Applicant accomplishes his purpose by providingva branch path from the receiving channel at a point in the system ahead of the detector, for instance from the .output circuit ofthe radio frequency amplifier; placing in this branch path a quartz crystalwhich lfilters out thevoce side-bands; amplifying the carrier current; rectifying the carrier energy, and causing variations of the carrier intensity automatically to produce offsetting variations of the negative biasing voltage on the grid of the detector,'whereby the output volume of the detector. is maintained substantially constant. A

Applicants invention not only overcomes fading due to variations of the carrier intensity, as does Aifels, but it overcomes fading without any likelihood of singing in the system, and by virtue of this feature of applicants arrangement, there is provided com- .pensation'for a greater variation of carrier amplitude. These and other advantages of the invention will appear more clearly hereinafter.

Applicants invention will be more clearly understood when the following detailed del scription is read with reference to the accompanying drawing. Figure 1 of the drawing shows diagrammatically the circuit arrangements of the receiving system, including the v circuit means for effecting the volume control; Fig. 2 shows schematically the fiow in e5 the'system of the various currents, including the direct current for the volume-control.

With reference to thedetails of F ig."1, the

antenna 1, the transformer 2, the vacuum tube radio frequency amplifier 3, the transformer 4, the vacuum tube detector 5, the transformer 6, andthe vacuumftube voice frequency amplifier 7 are elements ordinarily v found in radio receiving systems. Y

From the point8 in the plate circuit of the 75 radio frequency amplifier 3, applicant provides a lead to ground at 9, and places in this branch path of the amplifier output a quartz crystal 10 and the primary winding 11a `of the transformer 11. The secondary winding 11b of the transformer 11 serves as the input tothe vacuum tube amplifier 12, which` is inductively connected through the transformer'l to the vacuum tube14. In the plate circuit of the tube 14 is placed a resist- 85 ance 15,`from which a wire 16 leads to the grid circuit of the detector tube 5. 4

The operation of applicants system will now be descri ed, reference being had to Fig. 1 for a diagr mmatic showing of the appara- 90 tus involved, and to Fig. 2 for a schematic showing of yth current flow in the system. The incoming radio signals are amplified in the'tube 3. There are two possiblevchannels in the output circuit of this amplifier, the one `into the detector 5 and the other through the quartz crystal 10l into the amplifier 12. The resonance properties of the quartz crystal 'are clividedly marked. The device serves as a filter, beginning to cut oifyfrequencies ten 10.0

cycles to either side of the carrier, and frequencies of approximately sixty cycles to elther side of the carrier are greatly attenuated. Consequentl the cr stal serves to filter out the voice si e-band` refiencies and to pass the carrier frequency. n accordance with applicants arrangement, the carrier current output of the crystal filter 10 is amlilied in the tube 12, and the carrier energy 1s then rectified-or translated into lone-way energy-in the tube 14. The flow of pulsating current through the resistance 15 in the plate circuit of the tube 14 reacts on the detector 5 by virtue of the circuit arrangement shown and described above. More specifically, variations of the carrier intensity cause responsive variations in the amountl of negative biasing on the grid of the detector tube 5, because of the voltage drop in the resistance 15, in the plate circuit of the tube 14. Thus, when the carrier intensity increases, there is automatically produced an increase of the negative voltage on the grid of the -tube 5 l because of the increase of late current in the '.tube14, and, as is well un erstood in the art,

this increased negativevoltage serves to reduce the current flow in the plate circuit of the detector tube. Consequently, the output level of the detector is lowered. Conversely,

1a decrease of carrier intensity automatically produces a decrease of the negative voltage on the detector grid and an increase of the detector output volume. It follows of course that this control of the output level of detector tube 5 likewise controls the speech input to -the voice freqiency amplifie cants invention has been dis- While app iic embodiment which is closed in onev i deemed desirab e, it is to be understoodv that Ait is caable of embodiment in many other and di vscope of the invention as defined Apended claims.

erent forms within the spirit land Aby the ap.-v

' What is claimed is: f

1. In a radio receiving system, a threeelectrode vacuum tube detector, means in' cluded in the stem ahead of the detector for drawing o? a part of the carrier frequency and the voice side-band frequencies combined and for separating the carrier frequency from the voice side-band frequencies, and means for controlling the biasing voltage on the grid of the detector in response to and as an oset to variations of the carrier intensity.

2. In a radio receiving system, a three-electrode vacuum tube detector, means ahead of the detector for passing a part ofthe carrier frequency and the voice side-band frequencies 'combined into a branch path, means for passergy, and means responsive tothe current iowing in the output of said rectifying means for controlling the biasing voltage on the grid of the detector.

3. Ina radio receiving system, a detector the carrier energy, an meansl for contro 'ng the .output volume of the detector by oset- 'ting therein variations of the carrier intensit.

4. In a radio receivingl system including a three-electrode vacuum tube detector, the' method of controlling the output volume of the detector which consists in passing a part of the carrier frequency and the voice sideband frequencies combined into a branch ath before detection, passing the balance o the carrier frequency and the voice side-band frequencies combined to the input of the detector, ilterin out in said branch path the voice side-band requencies, 'rectifying the carrier energy, and causing variations of the carrier intensity to produce offsetting variations of the biaslng voltage on the grid of the detector.

5. In a radio receiving system, a main path, a detector in said main path, a path branching from the main path at a int ahead of the detector, a quartz crysta l filter in the branch path for eliminating from said branch path the voice side-band frequencies and pass- 1ng the carrier frequency, means for rectifying the carrier energy, and means responsive to the current owing in the output ofsaid rectifyin means for controlling the output volume o the detector.

6; In a radio receiving system, `a main path, a three-electrode vacuum tube detector in said main path', a path branchin from the main path at a point ahead of the etector, a quartz crystal filter in the branch 'ath for eliminating from said branch path t e voice side-band frequencies and passing the carrier frequency, means for rectifying the carrier energy, and means for increasing and decreasing .the negative biasing voltage on the grid of the detector `in response to increases and decreases, respectlvely, of the current `in the 'output of said rectifying means.

In testimony whereof, I have signed my name to this specification thisv 18thv day of ing the balance of the carrier -frequency andl voice side-band frequencies combined-to the input of the detector. means in said branch .path forflterin11r out the voice side-band frequencies, means for rectifying the carrier enlll 

